Birth complications have medical and neurobehavioral consequences. In the United States, birth complications of unknown origin continue to account for at least 50% of the reported cases. The proposed project is designed to examine the contribution of maternal stress to adverse birth outcomes. In addition, neuroendocrine response (beta-endorphins, ACTH, cortisol, CRF, and catecholamines) and measures of fetal physiology will be assessed as possible markers of stress and predictors of outcome. Over a three year period, 375 women, half Hispanic, and half Anglo, selected from a total population of over 7,200 will be assessed during the third trimester of their pregnancy with measures of stress and strain (response to stress). In addition, maternal plasma will be collected for assays of beta-endorphins, ACTH, CRF and cortisol, and maternal urine for catecholamines. These peptides have been selected because they are responsive to stress, and have effects on the course of pregnancy and birth outcome. Measures of fetal physiology, including doppler velocimetry of the uteroplacental circulation and fetal heart rate under resting and challenge conditions will be taken. At birth, maternal and cord (infant) blood will be collected and analyzed for levels of neuropeptides. Birth and delivery outcomes will be determined. Multivariate models to predict the effects of stress and strain on birth complications will be constructed.